Writing data into, and erasing data from, a flash memory requires an electrical current that is provided by a voltage source known as a “charge pump”. Briefly, a charge pump, as used in a flash memory, is an electric circuit that generates a relatively high voltage that is used to manipulate the amount of electrical charge within flash memory cells to write new data into these cells, to erase data from memory cells, and to read data from these cells. Being a voltage source, a charge pump is designed to provide an electrical current whose value is permitted to change from zero to some maximal value beyond which the level of the output voltage of the charge pump starts to decrease uncontrollably.
It may occasionally occur that, in a storage system that includes several storage devices, storage operations (e.g., writing data and erasing data) may need to be performed simultaneously in two or more storage devices. However, for the reason stated above, writing data into, and erasing data from, several storage devices simultaneously is limited by the maximum current that can be provided by the charge pump and, with more than one storage device operating simultaneously typically on peak current consumption level, there is a danger that the total current that is consumed by these storage devices would exceed the maximum allowable current. Under such circumstances, the voltage provided to the storage devices from a power supply or from the charge pump will drop below a valid operation level, causing the storage device to behave unpredictably. In such a case, the data that was last programmed to the storage device could be lost.
There is, therefore, a need to for a storage system that can perform multiple storage operations simultaneously in a controlled manner, without jeopardizing the operating voltage level associated with such operations.